A gas turbine engine may be used to power various types of vehicles and systems. A particular type of gas turbine engine that may be used to power aircraft is a multi-spool gas turbine engine. A typical multi-spool gas turbine engine may include, for example, at least three major sections—a compressor section, a combustor section, and a turbine section.
In a multi-spool engine, the compressor section may include two or more compressors. For example, in a dual spool engine, the compressor section may include a high pressure compressor, and a low pressure compressor. No matter the particular number of compressors it includes, the compressor section raises the pressure of the air drawn into the engine to a relatively high level. The compressed air from the compressor section then enters the combustor section, where fuel nozzles inject a steady stream of fuel. The injected fuel is ignited, producing high-energy gas.
The high-energy gas from the combustor section then flows into and through the turbine section, causing rotationally mounted turbine blades to rotate and extract energy. The air exiting the turbine section is exhausted from the engine, and the energy remaining in this exhaust may be used to generate thrust. Similar to the compressor section, in a multi-spool engine the turbine section may include a plurality of turbines. For example, in a dual spool engine, the turbine section may include a high pressure turbine and a low pressure turbine. The energy extracted from each of the turbines may be used to power other portions of the engine. For example, the low pressure turbine may be used to power the low pressure compressor via a low pressure spool, and the high pressure turbine may be used to power the high pressure compressor via a high pressure spool that is concentric to the low pressure turbine spool. The high and low pressure turbines may also be used to power external systems and components.
The gas turbine engine components that are configured to rotate, namely the compressors and turbines, may be rotationally mounted within the engine using bearings. For example, in a multi-spool gas turbine engine, a high pressure spool aft bearing in conjunction with a thrust bearing may be used to rotationally mount the high pressure spool, and thus rotationally support the high pressure compressor and high pressure turbine.
In some gas turbine engines, the high pressure spool aft bearing is located in a sump forward of the high pressure compressor. Thus, the high pressure compressor and high pressure turbine are overhung aft of the high pressure spool aft bearing. This relatively large overhung mass aft of the high pressure spool aft bearing can produce undesirable rotordynamic excursions, which can cause increased turbine clearances, and significantly reduced engine performance. In some other gas turbine engines, the high pressure spool aft bearing is located in a sump between the high pressure compressor and high pressure turbine, which reduces the overhung mass aft of the bearing. As a result, the rotordynamic excursions may be significantly reduced, and turbine clearances and engine performance may improve.
Although the latter engine configuration described above does provide improved engine performance, it does suffer certain drawbacks. For example, the sump seals are buffered using air from either the high pressure compressor impeller inlet or outlet. Because the air in the high pressure compressor is relatively hot, it can thermally stress the sump and sump seals, and/or cause coking of the sump seals, and/or result in undesirable heat input to the lubricant in the sump, and/or undesirable thermal heat rejection from the high pressure compressor air. Moreover, diverting high pressure air from the high pressure compressor can adversely impact engine performance.
Hence, there is a need for a gas turbine engine that is configured with a reduced overhung mass on the high pressure spool aft bearing, and/or that does not rely on air from the high pressure compressor to buffer the bearings of the sump in which the high pressure spool aft bearing is located and/or reduces thermal stresses on the sump and/or seals, and/or improves engine performance. The present invention addresses one or more of these needs.